Field emission lamp

ABSTRACT

A field emission lamp, capable of preventing the degradation and the non-uniformly distribution of the light intensity of the emitted light, even after long-term usage of the field emission lamp, is disclosed. The anode of the disclosed field emission lamp is not required to be transparent. The disclosed field emission lamp comprises: a transparent shell; an anode unit set inside the transparent shell; a cathode unit set between the anode unit and the transparent shell; and a phosphor layer set above the anode unit. The cathode unit is apart from the phosphor layer with a certain distance. The phosphor layer and the anode unit are both surrounded by the cathode unit.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a field emission lamp and, moreparticular, to a field emission lamp enabling long-term usage withoutbrightness degradation and/or unfavorable light uniformity and enablingthe anode to be made of a conductive material without high transparency.

2. Description of Related Art

Reference with FIG. 1, a conventional field emission lamp comprises: atransparent shell 11, an anode unit 12, a cathode unit 13, and aphosphor layer 14, in which, the transparent shell 11 has an innersurface 111, and the anode unit 12 is set on a part of the inner surface111 of the transparent shell 11. The cathode unit 13 is fixed at thecentral part of the transparent shell 11 and is surrounded by the anodeunit 12. The phosphor layer 14 is set on the anode unit 12.

The cathode unit 13 is apart from the phosphor layer 14 with a certaindistance, the anode unit 12 and the cathode unit 13 each electricallyconnects to contact pins (not shown) and forms a loop with an outerdriving circuit (not shown), and therefore the field emission lamp canbe driven to provide light by receiving a driving voltage from the outerdriving circuit.

The transparent shell 11 is a transparent tube made of soda-lime glass.Besides, the anode unit 12 is made of ITO (indium-tin oxide) orcarbon-nanotube film, and the cathode unit 13 is a metal bar coveredwith carbon-nanotubes serving as the electron emitter.

However, a large quantity of electrons may accumulate in the phosphorlayer 14 after a long-term operation (with many electrons bombarding thephosphor layer 14) of the field emission lamp, and a coulomb agingeffect of the phosphor layer 14 may happen and cause brightnessdegradation and unsatisfactory uniformity of the light transmitted bythe field emission lamp. Reference with FIG. 1, since the light providedby the phosphor layer 14 passes through the anode unit 12 set in theinner surface 111 of the transparent shell 11, a certain transparency ofthe anode unit 12 is needed to ensure the luminous efficacy of the fieldemission lamp. However, complex steps are required for the forming ofthe transparent electrode compared with the forming of a metalelectrode, and the electrical conductivity of the produced transparentelectrode is usually lower than a metal electrode, therefore thelifetime of the applied field emission lamp will be negativelyinfluenced.

Therefore, it is desirable to provide an improved field emission lampenabling long-term usage without brightness degradation and/orunfavorable light uniformity and enabling the anode to be made of aconductive material without high transparency.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a field emission lampenabling long-term usage without brightness degradation and/orunfavorable light uniformity.

Another object of the present invention is to provide a field emissionlamp enabling the anode to be made of a conductive material without hightransparency.

Therefore, the present invention provides a field emission lampcomprising: a transparent shell; an anode unit set inside thetransparent shell; a cathode unit set between the anode unit and thetransparent shell; and a phosphor layer set above the anode unit,wherein the cathode unit is apart from the phosphor layer with a certaindistance, and the cathode unit surrounds the anode unit.

The present invention also provides a field emission lamp comprising: afirst substrate; a second substrate; an anode unit locating between thefirst substrate and the second substrate, wherein the anode unit is seton part of the surface of the first substrate; a phosphor layer locatesbetween the second substrate and the anode unit, wherein the phosphorlayer is set on the anode unit; and a cathode unit locates between thesecond substrate and the phosphor layer, wherein the cathode unit isapart from the phosphor layer with a certain distance.

According to the present invention, even with a long-term operation ofthe field emission lamp, the electrons accumulated in the phosphor layercan be drained efficiently by the anode unit surrounded by the phosphorlayer. Therefore, the coulomb aging effect incurred in the fieldemission lamp of the prior arts can be resolved, and the brightness andthe uniformity of the light transmitted by the field emission lamp canbe increased. Also, since the anode unit of the field emission lamp ofthe present example locates in the central part of the field emissionlamp (as shown in FIGS. 2, 3, and 4) or locates in a side of the fieldemission lamp (on the surface of the first substrate as shown in FIG.5), light emitted from the phosphor layer can be transmitted by thefield emission lamp without passing through the anode unit whereby theanode unit can be made of a conductive material without hightransparency, the manufacturing cost can be reduced, and the processsteps of the field emission lamp can be simplified.

Other objects, advantages, and novel features of the invention willbecome more apparent from the following detailed description when takenin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a conventional field emission lamp;

FIG. 2 is a schematic view of a field emission lamp of example 1 of thepresent invention;

FIG. 3 is a schematic view of a field emission lamp of example 2 of thepresent invention;

FIG. 4 is a schematic view of a field emission lamp of example 3 of thepresent invention;

FIG. 5A is a schematic view of a field emission lamp of example 4 of thepresent invention;

FIG. 5B is a top view of a cathode unit comprising a cathode and anelectron-emitting source of the example 4;

FIG. 6 is a top view of a cathode unit comprising a cathode and anelectron-emitting source of the example 5; and

FIG. 7 is a top view of a cathode unit comprising a cathode and anelectron-emitting source of the example 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference with FIG. 2, the field emission lamp of the present example 1comprises: a transparent shell 21, an anode unit 22, a cathode unit 23,and a phosphor layer 24. The anode unit 22 is set inside the transparentshell 21, the cathode unit 23 is set between the anode unit 22 and thetransparent shell 21, the cathode unit 23 is apart from the phosphorlayer 24 with a certain distance, and the cathode unit 23 surrounds theanode unit 22 and the phosphor layer 24.

In the present example, the cathode unit 23 is set on an inner surface211 of the transparent shell 21 as shown in FIG. 2. The anode unit 22and the cathode unit 23 each electrically connects to contact pins (notshown) and forms a loop with an outer driving circuit (not shown), andtherefore the field emission lamp can be driven to provide light byreceiving a driving voltage from the outer driving circuit.

In the present example, the transparent shell 21 is a transparent tubeand is made of soda lime glass. However, the transparent shell 21 mayalso be made of soda glass, boron glass, lead glass, quartz glass, oralkali-free glass. The cathode unit 23 is an ITO (indium-tin oxide)layer having carbon nanotubes mixed therein, but the cathode unit 23 mayalso be an IMO (indium molybdenum oxide) layer, an IZO (indium-zincoxide) layer, or a graphite thin film having carbon nanotubes mixedtherein. The anode unit 22 is made of metal such as stainless steel,aluminum alloy, or nickel alloy.

In the present example, a reflective layer 25 locating between thephosphor layer 24 and the anode unit 22 is further provided to increasethe luminous efficacy of the field emission lamp, in which thereflective layer 25 is an aluminum foil. Herein, the reflective layer 25may also be other metal foil having high reflectivity such as a goldfoil, a silver foil, or a tin foil.

Hence, even after long-term operation (with many electrons emitted fromthe cathode unit 23 bombarding the phosphor layer 24) of the fieldemission lamp, the electrons accumulated in the phosphor layer 24 can bedrained efficiently by the anode unit 22 surrounded by the phosphorlayer 24. Therefore, the coulomb aging effect incurred in the fieldemission lamp of the prior arts can be resolved, and the brightness andthe uniformity of the light provided by the field emission lamp can beincreased.

Reference with FIG. 2, since the anode unit 22 of the field emissionlamp of the present example locates in the central part of the fieldemission lamp, light emitted from the phosphor layer 24 can betransmitted from the field emission lamp without passing through theanode unit 22 whereas the anode unit 22 can be made of a conductivematerial without high transparency, the manufacturing cost can bereduced, and the process steps of the field emission lamp can besimplified.

Reference with FIG. 3, the field emission lamp of the present example 2comprises a transparent shell 31, an anode unit 32, a cathode unit 33,and a phosphor layer 34. The anode unit 32 is set inside the transparentshell 31, the cathode unit 33 is set between the anode unit 32 and thetransparent shell 31, the cathode unit 33 is apart from the phosphorlayer 34 with a certain distance, and the cathode unit 33 surrounds theanode unit 32 and the phosphor layer 34.

According to the present example, the cathode unit 33 is set on an innersurface 311 of the transparent shell 31 as shown in FIG. 3. The anodeunit 32 and the cathode unit 33 each electrically connects to contactpins (not shown) and forms a loop with an outer driving circuit (notshown), and therefore the field emission lamp can be driven to providelight by receiving a driving voltage from the outer driving circuit.

In the present example, the transparent shell 31 is formed in a hollowbulb shape and is made of soda-lime glass. However, the transparentshell 31 may also be made of soda glass, boron glass, lead glass, quartzglass, or alkali-free glass. The cathode unit 33 is an ITO (indium-tinoxide) layer having carbon nanotubes mixed therein, but the cathode unit23 may also be an IMO (indium molybdenum oxide) layer, an IZO(indium-zinc oxide) layer, or a graphite thin film having carbonnanotubes mixed therein.

The anode unit 32 comprises a glass rod 321 and an electrical conductivelayer 322 coated on the glass rod 321. In the present example 2, areflective layer 35 locating between the phosphor layer 34 and the anodeunit 32 is further provided to increase the luminous efficacy of thefield emission lamp, in which the reflective layer 35 is an aluminumfoil. Herein, the reflective layer 35 may also be another metal foilhaving high reflectivity such as a gold foil, a silver foil, or a tinfoil.

Hence, even after long-term operation (with many electrons emitted fromthe cathode unit 33 bombarding the phosphor layer 34) of the fieldemission lamp, the electrons accumulated in the phosphor layer 34 can bedrained efficiently by the anode unit 32 surrounded by the phosphorlayer 34. Therefore, the coulomb aging effect incurred in the fieldemission lamp of the prior arts can be resolved, and the brightness andthe uniformity of the light provided by the field emission lamp can beincreased.

Reference with FIG. 3, since the anode unit 32 of the field emissionlamp of the present example 2 locates in the central part of the fieldemission lamp, light emitted from the phosphor layer 34 can betransmitted from the field emission lamp without passing through theanode unit 32 whereby the anode unit 32 can be made of a conductivematerial without high transparency, the manufacturing cost can bereduced, and the process steps of the field emission lamp can besimplified.

Reference with FIG. 4, the field emission lamp of the present example 3comprises a transparent shell 41, an anode unit 42, a cathode unit 43,and a phosphor layer 44. The anode unit 42 is set inside the transparentshell 41, the cathode unit 43 is set between the anode unit 42 and thetransparent shell 41, the cathode unit 43 is apart from the phosphorlayer 44 with a certain distance, and the cathode unit 43 surrounds theanode unit 42 and the phosphor layer 44.

In the present example, the transparent shell 31 is formed in a helixform and surrounds the phosphor layer 44 and the anode unit 42 as shownin FIG. 4. The anode unit 42 and the cathode unit 43 each electricallyconnects to contact pins (not shown) and forms a loop with an outerdriving circuit (not shown), and therefore the field emission lamp canbe driven to provide light by receiving a driving voltage from the outerdriving circuit.

In the present example, the transparent shell 41 is a transparent tubeand is made of soda lime glass. However, the transparent shell 41 mayalso be made of soda glass, boron glass, lead glass, quartz glass, oralkali-free glass. The cathode unit 43 is a metal bar covered with theelectron emitter, wherein the electron emitter is preferablycarbon-nanotubes and the metal bar is preferably made of stainlesssteel, aluminum, or nickel. The anode unit 42 is preferably made ofmetal such as stainless steel, aluminum alloy, or nickel alloy.

In the present example 3, a reflective layer 45 locating between thephosphor layer 44 and the anode unit 42 is further included to increasethe luminous efficacy of the field emission lamp, in which thereflective layer 45 is an aluminum foil. Herein, the reflective layer 45may also be another metal foil having high reflectivity such as a goldfoil, a silver foil, or a tin foil.

Hence, even after long-term operation (with many electrons emitted fromthe cathode unit 43 bombarding the phosphor layer 44) of the fieldemission lamp, the electrons accumulated in the phosphor layer 44 can bedrained efficiently by the anode unit 42 surrounded by the phosphorlayer 44. Therefore, the coulomb aging effect incurred in the fieldemission lamp of the prior arts can be resolved, and the brightness andthe uniformity of the light transmitted from the field emission lamp canbe increased.

Reference with FIG. 4, since the anode unit 42 of the field emissionlamp of the present example 3 locates in the central part of the fieldemission lamp, light emitted from the phosphor layer 44 can betransmitted from the field emission lamp without passing through theanode unit 42 whereby the anode unit 42 can be made of a conductivematerial without high transparency, the manufacturing cost can bereduced, and the process steps of the field emission lamp can besimplified.

Reference with FIG. 5A, the field emission lamp of the present example 4comprises a first substrate 51, a second substrate 52, an anode unit 53,a phosphor layer 54, and a cathode unit 55. The anode unit 53 locatesbetween the first substrate 51 and the second substrate 52, and theanode unit 53 is set on part of the surface of the first substrate 52.The phosphor layer 54 locates between the second substrate 52 and theanode unit 53, and the phosphor layer 54 is set on the anode unit 53.The cathode unit 55 comprising a cathode 551 and an electron-emittingsource 552 locates between the second substrate 52 and the phosphorlayer 54, and the cathode unit 55 is apart from the phosphor layer 54with a certain distance.

In the present example, the first substrate 51 and the second substrate52 are each a glass sheet made of soda-lime glass, however, the firstsubstrate 51 and the second substrate 52 can also be made of soda glass,boron glass, lead glass, quartz glass, or alkali-free glass, which isnot specially limited. The anode unit 53 is made of metal such as silveror aluminum. The cathode 551 is made of ITO (indium-tin oxide), and theelectron-emitting source 552 may be a patterned carbon-nanotube film.

Reference with FIG. 5B, a top view of a cathode unit comprising acathode 551 and an electron-emitting source 552 of the present exampleis shown, in which the electron-emitting source 552 locating on thecathode 551 is formed in a multi-bar shape and is randomly distributedover the whole surface of the cathode 551. Alternatively, the multi-barshaped electron-emitting source 552 can be distributed on only parts ofthe surface of the cathode 551 if required.

Besides, in other examples, the patterned electron-emitting source mayhave other patterns such as a pattern with spots or a pattern withrings, as shown in FIGS. 6 and 7 respectively, in which FIG. 6 shows anelectron-emitting source of the example 5 of the present invention andFIG. 7 shows an electron-emitting source of the example 6 of the presentinvention. According to FIG. 6, the electron-emitting source 652 has apattern with spots that are randomly distributed over the whole surfaceof the cathode 651. According to FIG. 7, the electron-emitting source752 has a pattern with rings distributing over the whole surface of thecathode 751.

Herein, an adequate aperture ratio of the pattern of theelectron-emitting source should be considered. For example, when thetotal surface area of the patterned electron-emitting source increases(i.e. the aperture ratio of the patterned electron-emitting sourcedecreases), the amount of the electrons emitted from theelectron-emitting source is increased and therefore the brightness canbe increased. However, light emitted from the cathode may be largelyshielded by the electron-emitting source while the total surface area ofthe patterned electron-emitting source increases. Therefore, theadequate aperture ratio of the patterned electron-emitting source shouldbe carefully considered.

Reference with FIG. 5A, the anode unit 53 and the cathode unit 55 eachelectrically connects to contact pins (not shown) and forms a loop withan outer driving circuit (not shown), and therefore the field emissionlamp can be driven to provide light by receiving a driving voltage fromthe outer driving circuit. In order to enhance luminous efficacy, areflective layer 56 locating between the phosphor layer 54 and the anodeunit 53 may be further provided in the present example 4, in which thereflective layer 56 may be an aluminum foil. Alternatively, thereflective layer 56 may also be another metal foil having highreflectivity such as a gold foil, a silver foil, or a tin foil.

Hence, even after long-term operation (with many electrons emitted fromthe cathode unit 55 bombarding the phosphor layer 54) of the fieldemission lamp, the electrons accumulated in the phosphor layer 54 can bedrained efficiently by the anode unit 53 surrounded by the phosphorlayer 54. Therefore, the coulomb aging effect incurred in the fieldemission lamp of the prior arts can be resolved, and the brightness andthe uniformity of the light transmitted by the field emission lamp canbe increased. Besides, reference with FIG. 5A, since the anode unit 53of the field emission lamp of the present example 4 locates in a side ofthe field emission lamp (on the surface of the first substrate 51),light emitted from the phosphor layer 54 can be transmitted from thefield emission lamp without passing through the anode unit 53 wherebythe anode unit 53 can be made of a conductive material without hightransparency, the manufacturing cost can be reduced, and the processsteps of the field emission lamp can be simplified.

According to the present invention, even after long-term operation ofthe field emission lamp, the electrons accumulated in the phosphor layercan be drained efficiently by the anode unit surrounded by the phosphorlayer. Therefore, the coulomb aging effect incurred in the fieldemission lamp of the prior arts can be resolved, and the brightness andthe uniformity of the light transmitted from the field emission lamp canbe increased. Also, since the anode unit of the field emission lamp ofthe present example locates in the central part of the field emissionlamp (as shown in FIGS. 2, 3, and 4) or locates in a side of the fieldemission lamp (on the surface of the first substrate as shown in FIG.5), light emitted from the phosphor layer can be transmitted from thefield emission lamp without passing through the anode unit whereby theanode unit can be made of a conductive material without hightransparency, the manufacturing cost can be reduced, and the processsteps of the field emission lamp can be simplified.

Although the present invention has been explained in relation to itspreferred embodiment, it is to be understood that many other possiblemodifications and variations can be made without departing from thescope of the invention as hereinafter claimed.

1. A field emission lamp, comprising: a transparent shell; an anode unitset inside the transparent shell; a cathode unit set between the anodeunit and the transparent shell; and a phosphor layer set above the anodeunit, wherein the cathode unit is apart from the phosphor layer, and thecathode unit surrounds the anode unit.
 2. The field emission lamp asclaimed in claim 1, wherein the cathode unit is set on an inner surfaceof the transparent shell.
 3. The field emission lamp as claimed in claim1, wherein the transparent shell is made of soda lime glass, soda glass,boron glass, lead glass, quartz glass, or alkali-free glass.
 4. Thefield emission lamp as claimed in claim 1, wherein the cathode unit isin a helix form and surrounds the phosphor layer and the anode unit. 5.The field emission lamp as claimed in claim 1, wherein the cathode unitis a transparent electrical conductive layer having carbon nanotubesmixed therein.
 6. The field emission lamp as claimed in claim 5, whereinthe transparent electrical conductive layer is an IMO (indium molybdenumoxide) layer, an IZO (indium-zinc oxide) layer, or a graphite thin film.7. The field emission lamp as claimed in claim 1, wherein the anode unitis made of metal.
 8. The field emission lamp as claimed in claim 1,wherein the anode unit is a glass rod coated with an electricalconductive layer.
 9. The field emission lamp as claimed in claim 1,further comprising a reflective layer locating between the phosphorlayer and the anode unit.
 10. The field emission lamp as claimed inclaim 9, wherein the reflective layer is made of aluminum, gold, silver,or tin.
 11. The field emission lamp as claimed in claim 1, wherein thetransparent shell is a transparent tube.
 12. The field emission lamp asclaimed in claim 1, wherein the transparent shell is formed in a hollowbulb shape.
 13. A field emission lamp, comprising: a first substrate; asecond substrate; an anode unit locating between the first substrate andthe second substrate, wherein the anode unit is set on part of thesurface of the first substrate; a phosphor layer locating between thesecond substrate and the anode unit, wherein the phosphor layer is seton the anode unit; and a cathode unit locating between the secondsubstrate and the phosphor layer, wherein the cathode unit is apart fromthe phosphor layer.
 14. The field emission lamp as claimed in claim 13,wherein the cathode unit is set on a part of the surface of the secondsubstrate.
 15. The field emission lamp as claimed in claim 13, whereinthe cathode unit comprises a cathode and an electron-emitting sourcelocating on a part of the surface of the cathode unit.
 16. The fieldemission lamp as claimed in claim 15, wherein the electron-emittingsource is a patterned carbon-nanotube film, and the patternedcarbon-nanotube film has a pattern with spots, a pattern with bars, or apattern with rings.
 17. The field emission lamp as claimed in claim 13,wherein the first substrate and the second substrate are independentlymade of soda lime glass, soda glass, boron glass, lead glass, quartzglass, or alkali-free glass.
 18. The field emission lamp as claimed inclaim 13, wherein the cathode unit is a transparent electricalconductive layer having carbon nanotubes mixed therein.
 19. The fieldemission lamp as claimed in claim 18, wherein the transparent electricalconductive layer is an IMO (indium molybdenum oxide) layer, an IZO(indium-zinc oxide) layer, or a graphite thin film.
 20. The fieldemission lamp as claimed in claim 13, wherein the anode unit is made ofmetal.
 21. The field emission lamp as claimed in claim 13, furthercomprising a reflective layer locating between the phosphor layer andthe anode unit.
 22. The field emission lamp as claimed in claim 21,wherein the reflective layer is made of aluminum, gold, silver, or tin.